The present invention relates to a tape cassette for use with a magnetic recording/reproducing device such as a video tape recorder, and more particularly to a short-time recording tape cassette including a small-diameter roll of a magnetic tape to permit a compact construction of the recording/reproducing device.
In a conventional tape cassette for use with a magnetic recording/reproducing device such as a video tape recorder (VTR), it has been proposed that a roll diameter of a magnetic tape contained in a cassette case of the tape cassette is reduced to define a large mouth section for receiving a head drum, thereby making the recording/reproducing device compact. Such a tape cassette is called a short-time recording tape cassette (as disclosed, for example, in Japanese Patent Laid-open Publication No. 60-171684 or Japanese Utility Model Application No. 62-14573 filed by the present assignee).
Such a conventional short-time recording tape cassette will be schematically described with reference to FIG. 15. Referring to FIG. 15 which is a top plan view of the tape cassette with an upper half thereof removed, reference numeral 51 generally designates a cassette case accommodating a pair of rotatable tape reels 52 and 53 around which a magnetic tape T is wound. A pair of semicolumnar tape guides 54a and 54b are provided at left and right front end portions of the cassette case 51. The magnetic tape T is guided through the tape guides 54a and 5b, and is exposed to a front opening of the cassette case 51 under a stretched condition as shown by a chain line. Further, a bottom wall of the cassette case 51 is largely recessed from its front end, so as to form a mouth section (opening) 55 between and front of both the tape reels 52 and 53.
In the tape cassette as constructed above, a diameter of each of the tape reels 52 and 53 is smaller than that of tape reels in a normal tape cassette as standardized. Accordingly, the mouth section 55 is larger in size than that in the normal tape cassette by an amount corresponding to the reduced diameter of the tape reels 52 and 53.
In the operation of this tape cassette, the magnetic tape T is drawn out frontward by a pair of draw-out guides 60a and 60b provided in the recording/reproducing device. Simultaneously, a head drum 61 and a tape running unit 62 (inclusive of an impedance roller 63, tape guides 64, 65 and 66, loading posts 67 and 68, capstan 69, pinch roller 70, etc.) provided in the recording/reproducing device are inserted into the mouth section 55. Under this condition, the magnetic tape T exposed at the front opening of the cassette case 51 is wound around the head drum 61 as shown by a solid line (i.e., loaded condition), thus carrying out a recording or reproducing operation.
According to this construction, as the size of the mouth section 55 is made larger by a reduced diameter of each of the tape reels 52 and 53, the head drum 61 and the like can be deeply inserted into the cassette case 51, thereby advantageously contributing to the compactness of the recording/reproducing device.
However, in the conventional short-time recording tape cassette, the enlargement of the mouth section is effected merely by reducing the diameter of each tape reel. Accordingly, the size of the mouth section can only be made so large, causing a limitation of the compactness of the magnetic recording/reproducing device.
As to an internal structure of this conventional short-time recording tape cassette, there is a dead space on the lateral and rear sides of the tape reels in the cassette case. That is, the whole space in the cassette case is not effectively utilized.
Further, in general, such a tape cassette employs a reel presser spring for biasing the tape reels, and it is necessary to maintain the biasing force of the spring against the tape reels at a substantially constant value, so as to stabilize rotation of the tape reels.